Recent work has demonstrated that certain medications currently used in ophthalmology are capable of altering both the physiologic function and anatomic appearance of the corneal endothelium. The purpose of this investigation is to define the physiological changes produced in the corneal endothelium by several ophthalmic preparations during in vitro perfusion in the specular microscope. These studies will establish the toxic dose levels of the agent tested as well as dose response curves. Transmission and scanning electron microscopy will be utilized to define anatomical and ultrastructural changes in the endothelium and be correlated with the physiological changes. Compounds to be investigated include: the preservatives benzalkonium chloride, chlorobutanol and thimerosal, the cationic surfactant cetyl pyridinium chloride, the enzyme Brinolase, and antiviral agents adenine arabinoside and hypoxanthine arabinoside.